Tap changing electrical control apparatus



May 3l, 1955 w. J. WILLIS ETAL TAP CHANGING ELECTRICAL CONTROL APPARATUS 3 Sheets-Shaml l Filed May l5, 1953 INVENTORS William J.

May 31, 1955 w. J. wlLLls ETAL 2,709,777

TAP CHANGING ELECTRICAL coNTRoL APPARATUS Filed Nay 15, 1955 :s sheets-shea*b 2 May 3l, 1955 w. J. wlLLls ETAL 2,709,777

TAP CHANGING ELECTRICAL CONTROL APPARATUS Filed may 15, 195s 5 Sheets-Sheet 3 wnNEssEs: mvENToRs dzvjdad, wimamuwims United States TA? CHANGNG ELECTRICAL CONTRGL APPARATUS 1953, sensi N0. 355,314

is cunas. (ci. 32a- 435) Application May This invention relates to transformer tap-changers and more particularly to control apparatus therefor'.

ln many instances it is desirable to return the output voltage of a tapped transformer to a given value. This can be accomplished by manually operating a tapchanger associated with the transformer so as to obtain the given output voltage. However, if the output voitage of the tapped transformer is being returned to a given value so as to match the output voltage of a transformer which is to be paralleled with the tapped transformer, it is often times difficult to obtain a proper match of the output voltages if this matching is to be done manually. This is mainly true if the operator who is manually operating the tap-changer is inexperienced. If an improper match of the output voltages of the two transformers being paralleled is obtained, circulating currents will iow between the transformers thereby possibly damaging them. Further, the manual actuation of a tap-changer to a given position requires the presence of an operator who must be on duty to actuate the tapchanger in accordance with various paralleling or load requirements.

An object of this invention is to provide for actuating a motor-driven transformer tap-changer `to a preselected position, by so interconnecting the tap-changer motor with a switch that rotates in accordance with the positioning of the tap changer and with a selector switch which is set to a position corresponding to the voltage setting of the transformer that an energizing circuit to the tap-changer motor is interrupted once the rotating switch reaches a position corresponding to the preselected position of the selector switch.

Another object of this invention is to provide for automatically matching the output voltage of a tapped transformer, having a tap-changer associated therewith, with the output voltage of another transformer so that the two transformers will operate properly in parallel, by rendering a novel combination responsive to the load on the tapped transformer so that the tap-changer is automatically actuated to a given position once the load on the tapped transformer reaches a predetermined value to thereby obtain a proper match of the output voltages of the two transformers.

A further object of this invention is to provide for actuating a motor-driven transformer tap-changer to a preselected position once a predetermined time is reached, by rendering a novel combination responsive to a timing device so that the tap-changer is automatically actuated to the preselected position once the predetermined time is reached.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

Figure l is a schematic diagram of circuits and appa ratus illustrating an embodiment of this invention and in which control apparatus is provided for automatically paralleling two transformers.

Fig. 2 is a schematic diagram of circuits and apparatus arent O illustrating another embodiment of this invention and in which control apparatus is provided for effecting an actuation of a tap-changer to a preselected position at a predetermined time, and

Fig. 3 illustrates an interconnected rotating switch and a selector switch which can be substituted for the interconnected rotating switch and selector switch illustrated in Figs. l and 2.

Referring to Fig. l, there is illustrated an embodiment of the teachings of this invention. As illustrated, control apparatus 34 is provided for performing two functions, one of the functions being to regulate the output voltage of a tapped autotransformer 35 when disconnected from a transformer 36. The other function is to simultaneously connect the transformer 36 in parallel circuit relationship with the autotransformer 35 and return the output voltage of the transformer 35 to a preselected value so as to obtain a proper match of the output voltages of the transformers 35 and 3o and thereby prevent the circulation of current between the transformers 35 and 36.

ln general, the control apparatus for regulating the output voltage of the transformer 35 comprises a tapchanger 37, a primary relay 38 responsive to the output voltage of the transformer 3S, control relays 39 and 49 responsive to the operation of the primary relay 3S for controlling reversible drive means, more particularly, a reversible capacitor type motor 4l, which is connected to the tap-changer 37 for actuating it in either direction to thereby maintain the output voltage of the transformer 35 substantially constant. On the other hand, the control apparatus for eecting an actuation of the tapchanger 37 to a preselected position so as to obtain a given output voltage for the transformer 3S comprises in general a rotating switch l2 mechanically connected to the motor el. so as to rotate and determine the positioning of the tap-changer 37. The rotating switch d2 comprises a plurality of stationary contacts l through 3.3 which correspond to the thirty-three positions of the tapchanger 37, as will be described hereinafter. A rotating contact 43 is mechanically connected to the motor l so as to rotate in accordance with the positioning of the tap-changer 37 and selectively engage the stationary contacts 1 through 33 as the rotating switch 42 is actuated through positions i to 33. In particular, the rotating contact 43 is mechanically connected through suitable gearing 45 and mechanical connections i7 and i9 to the motor 4l in order that the rotating contact 43 is actuated through one position when the tap-changer 37 is actuated through one tap-changing position.

ln order to preselect the position to which the tapchanger 37 is to be returned once the load on the transformer 35 reaches a predetermined value, a selector switch 5t) is provided. As illustrated, the selector switch 5t) comprises a plurality of stationary contacts i through 33' which likewise correspond to the thirty-three positions of the tap-changer 37, the stationary contacts i through 33 being electrically connected to the corresponding stationary contacts l through 33 of the rotating switch 42. Two rotatable electrically conducting segments 52 and S-tare disposed to make electrical contact with all but one of the stationary contacts l through 33 irrespective of the positioning of the segments 52 and Sri. As illustrated, an insulating member 56 is associated with the segments 52 and 54 in order to electrically insulate the segment 52 from the segment 54. ln practice, the insulating member 56 also serves as n means for rotating by hand the segments S2 and .f5-'l to the desired preselected position.

From the above statement that the segments 52 and 5d are disposed to make electrical contact with all but one of the associated stationary contacts l through 33 it avea??? follows that each of the segments 52 and 54 must be such as to be capable of bridging thirty-two of the stationary contact members, 1 through 32' or Z. through 33'. in order to electrically connect the segments 52 and 54 of the selector switch 5t) to the control relays 4i) and 39 irrespective of the positioning of the segments 5.2 and 54, brushes 6i? and 62 are disposed to make electrical contact with the segments 52 and 54, respectively.

in this instance, the control relay 39 comprises an operating coil 63 and contact members 64 and 65 which are disposed to be actuated into and out of engagement with their associated stationary contacts. On the other hand, the control relay 40 comprises an operating coil 66 and contact members 67 and 63 which are disposed to be actuated into and out of engagement with their 1 associated stationary contacts. Circuit means, which will be set forth in the description of the operation, is provided for interconnecting the rotating contact 43 of the rotating switch 42 and, at any given position of the segments 52 and 54, all but one of the stationary contacts 1 through 33 of the selector switch 5i? with the operating coils 63 and 66 and with a source of alternating current, as applied to the terminals 70 and 71, so that the operating coils 63 and 66 of the relays 39 and 4t), respectively, are rendered responsive to the positioning of the rotating contact 43 of the rotating switch 42. The relays 39 and 49 in turn control the operation of the motor 41 so as to return the tap-changer 37 to a position corresponding to a preselected position set on the selector switch i). In particular, the relay 39 is so connected to the motor 41 that when its operating coil 63 is energized an electrical circuit is completed to the motor 41 to effect a rotation of the motor 41 in such a direction as to decrease the output voltage of the transformer 35, as will be explained more fully hereinafter. On the other hand, the relay 4t? is so connected to the motor 41 that when its operating coil 66 is energized an electrical circuit is completed to the motor 4l to effect a rotation of the motor 41 in such a direction as to increase the output voltage of the transformer 35, as will be explained more fully hereinafter.

The primary relay 38 which is utilized in regulating the output voltage of the transformer comprises an operating coil 72 which is responsive to the output voltage of the tapped transformer 35. ln particular, the operating coil 72 is electrically connected to the output terminals 73 and 74 of the transformer 35. A movable contact 75 is disposed to be actuated in accordance with the magnitude of the voltage across the operating coil 72 thereby selectively engaging either the stationary contact 76 or the stationary contact 77 of the primary relay 3S. As will be explained more fully hereinafter in the operation of the apparatus, when the movable contact 75 is actuated into engagement with the stationary contact 76 the relay 39 effects a decrease in the output voltage of the transformer 35. On the other hand, when the movable contact 75 is actuated into engagement with the stationary contact 77 the relay 40 effects an increase in the output voltage of the transformer 35.

Referring more particularly to the autotransformer 35, it is to be noted that the transformer 35 includes a fixed winding 78 and a tapped winding 79, which receive energy from the supply terminals si) and 73 and supply energy to the load terminals 74 and 73, the terminal 73 functioning as both a load and supply terminal. ln order to vary the amount of the tapped winding 79 that is connected in circuit relationship with the fixed winding 78, the tap changer 37 is electrically connected to the tapped winding 79 and to the fixed winding 7? of the transformer 35.

In this instance, the tap-changer 37 includes two mov` able contact members or tap-changer arms 81 and 32 which are actuated by the motor 41 through the gearing and the mechanical connections 49 and 33. As can be seen from the drawings, one end of the movable coniii) tact member 8l remains in electrical contact with a conducting ring 84 when the contact member Sl is being actuated into its various positions around the ring 84 by means of the motor 41. As the movable contact member 81 is being actuated through its various positions, the other end of the contact member Si selectively engages a plurality of stationary contact members 85, 36, 87, SS, 89, 90, 91, 92 and 93, which are electrically connected to the tapped winding 79 of the transformer 35. In like manner, one end of the movable contact member 82 engages these stationary contact members S5 through 93 as it is actuated through its various positions. However, the other end of the movable contact member 82 during these various positions remains continually in electrical contact with a conducting ring 94.

In order to connect the tapped winding 79 so that its turns aid or buck the turns of the fixed winding 73, a reversing switch 97 is provided. In this instance, the reversing switch 97 comprises two stationary contact members 98 and 99 which are selectively engaged by a movable contact member l0@ which is mechanically connected to the gearing 45. As illustrated, the stationary contact member 9S is electrically connected to one end of the tapped winding 79 and the stationary contact 99 is electrically connected to the other end of the tapped Winding 79.

For the purpose of interconnecting the fixed winding 7S with the tapped winding 79, one end of the fixed winding 78 is electrically connected to the movable contact member 10i) of the reversing switch 97. As can be seen from Fig. l, the load terminal 74 is also electrically connected to the movable contact member 100 as well as to the stationary contact member of the tap-changer 37. As illustrated, a preventive autotransformer 102 is electrically connected to the conducting rings 84 and 94, through conductors itl-4 and 3.06, respectively, in order to prevent an excessive flow of current through the bridged portion of the winding 79 and excessive arcing at the moving contacts 81 and S2.

The output voltage of the autotransformer 35 as it appears across the load terminals 73 and 74, is at a minimum when the movable contact members 8i and 32 of the tap-changer 37 are both in electrical contact with the stationary contact member 93, and the movable contact member litt? of the reversing switch 97 is in electrical contact with the stationary contact member 99. ln orderrto increase the output voltage of the transformer 35, the relay 4i) effects a rotation of the motor 41 in such a direction as to actuate the movable contact member Si into engagement with the stationary contact member 92. The output voltage of the transformer 35 is further increased by effecting a rotation of the motor 4l in the same direction by means of the relay 4i) to thereby also actuate the movable contact member 82 into engagement with the stationary contact member 92. By continuing this sequence of positioning of the movable contact members S1 and 82 in the same direction, the contact members Si and 82, reach the position where they both engage the stationary contact member 36. Up to this position, the turns of the tapped winding 79 aid the turns of the iixed winding 78. On further rotation of the motor 41 in the same direction, the movable contact member Sl makes electrical Contact with the stationary contact member S5. However, as soon as the movable contact member S2 breaks contact with the stationary contact member 86 on further rotation of the motor 41 in the same direction, the movable contact member i of the reversible switch 97 is actuated by the gearing 45 so as to make electrical contact with the stationary contact member 93.

With both the movable contact members Si and 32 in electrical contact with the stationary contact member S5 and the movable contact member iti@ of the reversing switch 97 in electrical contact with the stationary contact member 98, the tap-changer 37 is in the neutral position in which the input and output voltages are substantially equal. By eiiecting a rotation of the motor 41 in the same direction, the output voltage of the transformer 35 is further increased since the turns of the tapped winding 79 are now bucking the turns of the xed winding 7S. The output voltage of the transformer 35 continues to increase as long as the motor 41 rotates in the same direction until finally both the movable contact members 81 and 82 engage the stationary contact member S6. This position of the tap-changer 37 represents the position of maximum output voltage for the transformer 35.

In order to insure a complete step operation of the tap-changer 37, a cam member 119 is mechanically connected to the gearing 45. 1n particular, the cam member 11i) holds a Contact member 112 in the closed position with respect to its associated stationary contacts when the tap-changer 37 is moving from one step to the next step. However, on completion of each step operation of the tap-changer 37, the cam member 116 permits the contact member 112 to become disengaged from its associated stationary contacts.

As hereinbefore mentioned, the transformer 36 is connected in parallel circuit relationship with the autotransforrner 35 when the load on the transformer 35 reaches a predetermined value. in particular, a contactor 116 is disposed to be responsive to load current of the transformer 35. The contactor 116 comprises a plurality of contact members 118, 120, 122, 124-, 126 and 32S and their associated stationary contacts. The contact members J8, 126i, 122, 124, 126 and 12S are actuated into and out of engagement with their associated stationary contacts in accordance with the current flow through an operating coil 139 of the contactor 1lb' which is responsive to the current output of a current transformer 132 which is disposed to be responsive to the load current of the transformer 35.

The operation of the apparatus illustrated in Figure l will now be described. With the apparatus positioned as shown in Fig. l, the output voltage of the transformer 35 is at its regulated value and the control apparatus 34 is disposed to regulate the output voltage of the transformer 35. With the control apparatus 34 disposed to regulate the output voltage of the transformerS, the transformer 36 supplies energy to the load conductors 136 and E33 and is not connected in parallel circuit relationship with the transformer 35.

Assuming the movable Contact members 81 and S2, of the tap-changer 37 are on position 32 as illustrated in Fig. l and assuming further that the load voltage of the transformer 35 decreases to a value below its regulated value so as to decrease the voltage across the operating coil 72 of the primary relay 33, the movable Contact 75 will be actuated into engagement with its associated stationary Contact 77 to thereby complete an energizing circuit to the operating coil 66 of the relay 50. The energizing circuit to the operating coil 66 of the relay 4G extends from the terminal iti through the contact member 128 of the contactor lio', an electrical conducting member 14@ of the primary relay 33, the movable contact 75, the stationary contact 77, and the operating coil 66 of the relay di), to the terminal 7l. The energization of the operating coil 66 of the relay llt) effects an actuation of the contact members 67 and 68 to the closed position, the closing of the contact member 67 establishing a holding circuit for the operating coil 66 which extends from the terminal 7G through the Contact member 112, the Contact member v57 of the relay 4d, and the operating coil 66 of the relay di?, to the terminal 7 With the Contact member 68 of the relay Liti in the closed position an energizing circuit is established to the motor 41 which extends from the terminal 71 through the contact member 63 of the relay di?, a capacitor '5.42 of the motor 41, and a winding Ztl-ifi of the motor 41, to the terminal 70, to thereby actuate the movable Contact 82 of the tap-changer 37 into engagement with the stationary contact member S6 and thus increase the output voltage of the transformer 35. if this restores the output voltage of the transformer 35 to its regulated Value, the primary relay 38 does not call for a further increase in the output voltage of the transformer 35. Of course, with the tap-changer 37 in position 33, it is not possible to further increase the output voltage of the transformer 35.

On the other hand, assuming the output voltage of the transformer 35 increases to a value above its regulated value, the voltage across the operating coil 72 of the primary relay 33 will be such as to effect an actuation of the movable contact 75 into engagement with its associated stationary Contact 76 to thereby complete an energizing circuit to the operating coil 63 of the relay which extends from the terminal 7i) through the Contact member H3 of the contacter H6, the conducting member Lid of the primary relay 3S, the movable contact 7.5, the stationary contact 76, and the operating coil 63 of the relay 39, to the terminal 71. The energization of the operating coil 63 of the relay 39 effects an actuation of the contact members 64 and 65 of the relay 39 to the closed position, the closing of the contact member 64 establishing a holding circuit for the operating coil 63 which extends from the terminal 7G through the contact member i12, the Contact member 64 of the relay 3%, and the operating coil 63, to the terminal 71. With the Contact member 65 of the relay 39 in the closed position, energizing circuit for the motor 41 is established which extends from the terminal 7?. through the contact member 65 of the relay 39, the capacitor 142 of the motor 41, and a winding 146 of the motor @i1 to the terminal 79 to thereby effect a rotation of the motor 41 in such a direction as to actuate the movable Contact member 81 of the tap-changer 37 into engagement with the stationary Contact member S7. Such an action decreases the output voltage of the transformer 3L'. if such a decrease in the output voltage of the transformer 35 is not suicient to return it to its reguiated value, the operating coil 63 of the relay 39 continues to remain energized to thereby effect a further actuation of the tapchanger 37 and thus a further decrease in the output voltage of the transformer 35 until it reaches its regulated value.

So far, the description of the operation of the apparatus iliustrated in Fig. l has been under the assumption that the load current of the transformer 35 is not of sufficient magnitude to effect a paralleling of the transformer 36 with the transformer 35, to thereby distribute the load between the transformers 35 and 36. However, assuming the load on the transrormer 35 does increase to such a value as to effect an actuation of the line contactor M6, then the contact members 12b, E24 and 126 of the contacter .H6 are actuated to the closed position to thereby connect the transformer 36 in parallel circuit relationship with the transformer 35 and electrically connect the erminal 7d to the rotating contact 43 of the rotating switch Such an operation of the contactor 116 also actus-.tes the Contact members 118, 12.2 and 128 to the open position to thereby electricaily disconnect the movable contact 75 of the primary relay 3S from the terminal 7d and thus render the control apparatus 34 inoperative from the standpoint of regulating the output voltage of the transformer 35.

As illustrated in Fig. l, the selector switch 5t) is set to position 17 with the Contact 17 not in engagement with either the segment 52 or the segment 54. However, it is to be understood that the selector switch can be set to any of the thirty-three positions. The position in which the selector switch 59 is set depends on many factors, such as the magnitude of the input voltage to the transformer 35 and the output voltage of the potential transformer 36 which in turn can be varied so as to obtain a desired output voltage when the transformers 35 and 36 are connected in parallel circuit relationship with one another. With the selector switch 50 set at position 17 and the contact member 126 of the contactor 116 in the closed position, the control apparatus 34 will eect a rotation of the motor 41 in such a direction as to return the tap-changer 37 from position 32 as illustrated in the drawing to position 17 to thereby match the output voltage of the transformer 35 with the output voltage of the transformer 36. In particular, with the rotating contact 43 disposed in position 32 as illustrated in Fig. l of the drawings, an electrical circuit is completed to the operating coil 63 of the control relay 39 which extends from the terminal 70, through the contact member 126 of the contactor 116, a conductor 150, the rotating contact 43 of the rotating switch 42, the stationary contact 32 of the rotating switch 42, the stationary contact 32 of the selector switch Si), the rotatable electrically conducting segment 54 of the selector switch 50, the brush 62, a conductor 152, and the operating coil 63 of the relay 39, to the terminal 71. The

energization of the operating coil 63 of the relay 39 elects an actuation of the contact members 64 and 65 to the closed position, the closing of the contact member 64 establishing a holding circuit for the operating coil 63 which extends from the terminal 7i) through the contact member 112, the contact member 64 of the relay 39, and the operating coil 63, to the terminal 71. With the contact member 65 of the relay 39 in the closed position, an energizing circuit is established for the motor 41 which extends from the terminal 71 through the contact member 65 of the relay 39, the capacitor 142 of the motor 41, and the winding 146, to the terminal 76, to thereby effect a rotation of the motor 41 in such a direction as to rotate the contact member 43 of the rotating switch 42 to position 31V and actuate the tap-changer 37 to position 31. The rotating switch 42 and the holding circuit for the operating coil 63 of the relay 39 continue to establish an energizing circuit to the operating coil 63 until the rotating Contact 43 and the tap-changer 37 are actuated to position 17. With the rotating contact 43 of the rotating switch 42 in position 17, the energizing circuit to the operating coil 63 of the relay 39 is interrupted since the stationary contact 17 of the selector switch Si) does not make electrical contact with the segment 52 or the segment 54 when they are positioned as shown in Fig. l. Therefore, when the rotating contact 43 reaches position 17, the motor 41 remains stationary and the tap-changer 37 remains in the preselected position 17.

If the selector switch 5t) is set to position 33 with the stationary contact 33 not making electrical contact with either the segment 52 or the segment 54 and the rotating contact 43 of the rotating switch 42 is in engagement with the stationary contact 32, the following operation takes place when the load on the transformer 35 reaches a predetermined value. The contact member 126 of the contactor 116 is actuated to the closed position to thereby complete an energizing circuit to the operating coil 66 of the control relay 4i? which extends from the terminal 70 through the contact member 126 of the contacter 116, the conductor 150, the rotating contact 43 of the rotating switch 42, the stationary contact 32 of the rotating switch 42, the stationary contact 32 of the selector switch Sil, the segment S2, the brush 6G, a conductor 154, and the operating coil 66 of the relay 4i), to the terminal 71. On energization of the operating coil 66, the contact members 67 and 68 of the relay 4G are actuated to the closed position, the closing of the contact member 67 establishing a holder circuit for the operating coil 66 which eX- tends from the terminal 7l) through the contact member 112, the Contact member 67 of the relay 46, and the operating coil 66, to the terminal 71. On the other hand, the closing of the contact member 68 of the relay 40 completes an energizing circuit to the motor 41 which extends from the terminal 71, through the contact member 68 of the relay dil, the capacitor'142 ol' the motor 41 and the winding 144, to the terminal 7l) to thereby effect on UU a rotation ofthe rotating contact 43 of the rotating switch 42 to position 33. When the rotating contact 43 rotates to position 33, the tap-changer 37 is simultaneously actuated to position 33. With the rotating contact 43 in position 33, the energizing circuit to the operating coil 66 of the relay 40 is interrupted since the stationary contact member 33 of the selector switch 5d does not make electrical contact with either the segment 52 or the segment 54. Therefore, the motor 41 remains stationary and the tap-changer 37 remains in the preselected position 33.

Referring to Fig. 2, there is illustrated another embodiment of this invention in which like components of Figs. 1 and 2 have been given the same reference characters. The main distinction between the apparatus illus- :rated in Figs. l and 2 is that in the apparatus of Fig. 2, the control apparatus is responsive to a timing device 2G63 to thereby actuate the tap-changer 37 to a preselected position as determined by the selector switch Si) once a preselected time is reached. Also, the transformer 36 and the control apparatus for connecting this transformer in parallel circuit relationship with the transformer 35, as illustrated in Fig. l, is not provided in the apparatus of Fig. 2. However, the apparatus illustrated in Fig. 2 is substantially the same as the remainder of the apparatus illustrated in Fig. l except that the operating coil 139 or the contacter 116 in Fig. 2 responds to the timing device 266 instead of to the load current of the transformer 3S as was the case in the apparatus illustrated in Fig. l. With the selector switch 50 set to position 17, as illustrated in Fig. 2, the tap-changer 37 will be actuated to the preselected position 17 at a given time as determined by the timing device 2436 in the same manner that the tap-changer 37 illustrated in Fig. 1 was actuated to position 17. Since the load on the transformer 35 is normally less between the hours of ll:00 p. m. and 6:00 m., the timing mechanism Zitti could be set so as to decrease the output voltage of the transformer 35 at 11:00 p. in. and return the output voltage to a higher value at 6:00 a. m.

Referring to Fig. 3, there is illustrated control apparatus that can be substituted for the rotating switch 42 and the selector switch 50 illustrated in Figs. l and 2, and in which like components ot' Figs. l, 2 and 3 have been given the same reference characters. The main distinction between the control apparatus illustrated in Fig. 3 and the corresponding control apparatus illustrated in Figs. l and 2 is that in the apparatus illustrated in Fig. 3, the switch Sil functions as a rotating switch instead of a selector switch, as illustrated in Figs. l and 2, and the switch 42 functions as a selector switch instead of a rotating switch as illustrated in Figs l and 2. ln Fig. 3, the mechanical connection 47 is connected to the insulating member 56 of the switch Sti so as to effect a positioning of the segments 52 and S4 in accordance with the positioning of the tap-changer 37. lt is to be noted that in the apparatus illustrated in Fig. 3 the gearing connected to the mechanical connection 47 is changed so as to rotate the switch Sti illustrated in Fig. 3 through a proportional fewer number of degrees than the switch 42 illustrated in Figs. l and 2 with each step operation of the tap-changer 37. It is also to be noted that in Fig. 3 the stationary contacts 1 through 33 of the switch Sii are numbered in the reverse direction as compared to the manner of numbering the stationary contacts ofthe switch 513 illustrated in Figs. l and 2. l

With the control apparatus illustrated in Fig. 3 substituted for the corresponding control apparatus illustrated in either Fig. l or 2, it is necessary to manually position the contact 43 of the switch 42 to position 17 in order to elect a return of the tap-changer 37 to position 17. Since the remainder of the operation of the apparatus illustrated in Figs. l and 2, with the apparatus illustrated in Fig. 3 incorporated therein, is substantiaily the same as the operation of the apparatus illustrated 9 in Figs. l and 2, a further description of such operation is deemed unnecessary.

The apparatus embodying the teachings of this invention has several advantages. For instance, in the apparatus illustrated in Fig. l an accurate matching of the output voltages of the transformers and 36 is obtained. Therefore, no damage is inflicted on these transformers. ln addition, the apparatus illustrated in the various embodiments is automatic and is not dependent upon the skill of an operator.

Since certain changes may be made in the above apparatus and circuits and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

l. In control apparatus for actuating a tap-changer arm to a preselected position so as to obtain a given output voltage from a transformer associated with the tapchanger arm, the combination comprising, reversible drive means connected to the tap-changer arm for actuating it in either direction to thereby vary the output Voltage of the transformer, a rotating switch mechani- 7' cally connected to said reversible drive means so as to rotate and determine the positioning of the tap-changer arm and comprising a plurality of stationary contacts corresponding to the positions of the tap-changer arm, a selector switch comprising a plurality or" stationary contacts corresponding to the positions of the tap-changer arm, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for interconnecting said rotating switch and said selector switch with said reversible drive means 'to thereby eitect a rotation of said reversible drive means in such a direction as to return the tap-changer arm to a position corresponding to a preselected position of said selector switch.

2. ln control apparatus for actuating a tap-changer to a preselected position so as to obtain a given output voltage from a 'transformer associated with the tapchanger, the combination comprising, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to etiect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to etiect a rotation of said motor in the opposite direction, a rotating switch mechanically connected to said motor so `as to rotate in accordance with the positioning of the rtap-changer -and comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, circuit means for interconnecting the stationary contacts of said rotating switch with the correv sponding stationary contacts of said selector switch, and further circuit means for interconnecting said rotating switch and said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

3. In control apparatus for actuating a tap-changer to a preselected position so as to obtain a given output voltage from a transformer associated with the tapchanger, the combination comprising, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotating contact mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and selectively engage said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the ositions of the tap-changer and two rotatable electricaly conducting segments electrically insulated from one nother and disposed to make electrical contact with all but one ot' the stationary contacts of said selector switch irrespective of the positioning of said segments, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for interconnecting the rotating contact of said rotating switch and, at any given position of said segments, all but one of the stationary contacts of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of the rotating Contact of said rotating switch to thereby effect a rotation ot said motor in such a direction as to return the tapchanger to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

4. ln control apparatus for actuating a tap-changer to a preselected position so as to obtain a given output voltage from a transformer associated with the tapchanger, the combination comprising, a reversible motor mechanicaliy connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the transformer, two relays each having an Operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to t. e positions o the tap-changer and two electrically conducting segments veiectrically insulated from one another and mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and always engage all but one of said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotatable contact for selectively engaging the stationary contacts of said selector switch, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for interconnecting, at any given position of said segments, all but one of the stationary contacts of said rotating switch and the rotatable contact of said selector switch with the operating coils of said relays and with a source of energy s that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

5. In control apparatus for properly paralleling a given transformer with a tapped transformer, the combination comprising, a tap-changer connected to the tapped transformer, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch mechanically connected to said motor so as to rotate in accordance with the positioning of the tapchanger and comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for paralleling said given transformer with said tapped transformer and for simultaneously interconnecting said rotating switch and said selector switch with the operating coils of said relays and with a source of energy so that 'the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby elect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

6. in control apparatus for properly paralleling a given transformer with a tapped transformer, the combination comprising, a tapchanger connected to the tapped transformer, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said 'motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrieal circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotating contact mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and selectively engage said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and two rotatable electrically conducting segments electrically insulated from one another and disposed to make electrical contact with all but one of the stationary contacts of said selector' switch irrespective of the positioning of said segments, circuit` means for interconnecting the staatonary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for paralleling said given transformer with said tapped transformer and for simultaneously interconnecting the rotating contact of said rotating switch and, at any given position of said segments, all but one of the stationary' contacts of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of the rotating contact of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

7. ln control apparatus for properly paralleling a given transformer with a tapped transformer, the combination comprising, a tap-changer connected to the tapped transformer, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that. when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corre: sponding to the positions of the tap-changer and two electrically conducting segments electrically insulated from one another and mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and always engage all but one of said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotatable contact for selectively engaging the stationary contacts of said selector switch, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means for parallelinU said given transformer with said tapped transformer and for simultaneously interconnecting, at any given position of said segments, all but one of the stationary contacts of said rotating switch and the rotatable contact of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

8. In control apparatus for automatically paralleling a given transformer with a tapped transformer once the load on the tapped transformer reaches a predetermined value, the combination comprising, a tap-changer connected to the tapped transformer, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means responsive to the load current of said tapped transformer for automatically paralleling said given transformer with said tapped transformer and for simultaneously interconnecting said rotating switch and said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive i3 to the positioning of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

9. In control apparatus for automatically paralleling a given transformer with a tapped transformer once the load on the tapped transformer reaches a predetermined value, the combination comprising, a tap-changer connected to the tapped transformer, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to eifect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotating contact mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and selectively engage said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and two rotatable electrically conducting segments electrically insulated from one another and disposed to make electrical contact with all but one of the stationary contacts of said selector switch irrespective of the positioning of said segments, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, and further circuit means responsive to the load current of said tapped transformer for automatically paralleling said given transformer with said tapped transformer and for simultaneously interconnecting the rotating contact of said rotating switch and, at any given position of said segments, all but one of the stationary contacts of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of the rotating contact of said rotating switch to thereby elfect a rotation of said motor in such a direction as to return the tapchanger to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

l. in control apparatus for automatically paralleling a given transformer with a tapped transformer once the load on the tapped transformer reaches a predetermined value, the combination comprising, a tap-changer connected to the tapped transformer, a reversible motor inechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the tapped transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to eifect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and two electrically conducting segments electrically insulated from one another and mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and always engage all but one of said stationary contacts, a selector sv itch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotatable Contact for selectively engaging the stationary contacts of said selector switch, circuit means for interconnecting the stationary contacts of said rotating switch v/th the corresponding stationary contacts of said selector switch, and further circuit means responsive to the load current of said tapped transformer for automatically paralleling said given transformer with said tapped transformer and for simultaneously interconnecting, at any given position of said segments, all but one of the stationary contacts of said rotating switch and the rotatable contact of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby effect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and. said selector switch cooperate to deenergize said motor.

ll. In control apparatus for actuating a tap-changer to a preselected position at a given time so as to obtain a given output voltage from a transformer associated with the tap-changer, the combination comprising, a reversible motor mechanically connected to the tapchanger for actuating it in either direction to thereby vary the output voltage of the transformer, two relays cach having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch connected to said motor so as to rotate in accordance with the positioning of the tap-changer and coinprising a plurality of stationary contacts corresponding to the positions of the tap-changer, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, a timingdevice, and further circuit means responsive to the timing device, for interconnecting said rotating switch and said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby eliect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

l2. in control apparatus for actuating the tap-changer to a preselected position at a given time so as to obtain a given output voltage from a transform associated with the tap-changer, the combination comprising, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and a rotating contact mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and selectively engage said stationary contacts, a selector switch comprising a plurality of stationary contacts corresponding to the positions of the tap-changer and two rotatable electrically conducting segments electrically insulated from one another and disposed to make electrical contact with all but one of the stationary contacts of said selector switch irrespective of the positioning of said segments, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, a timing device, and further circuit means responsive to the timing device for interconnecting the rotating contact of said rotating switch and, at any given position of said segments, all but one of the stationary contacts of said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of the rotating contact of said rotating switch to thereby eiect a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position of said selector switch, at which time said rotating switch and said selector switch cooperate to deenergize said motor.

13. In control apparatus for actuating a tap-changer to a preselected position at a given time so as to obtain a given output voltage from a transformer associated with the tap-changer, the combination comprising, a reversible motor mechanically connected to the tap-changer for actuating it in either direction to thereby vary the output voltage of the transformer, two relays each having an operating coil, one of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in one direction and the other of said relays being so connected to said motor that when its operating coil is energized an electrical circuit is completed to said motor to effect a rotation of said motor in the opposite direction, a rotating switch comprising a plurality of stationary contacts corresponding to the positions of the tapchanger and two electrically conducting segments electrically insulated from one another and mechanically connected to said motor so as to rotate in accordance with the positioning of the tap-changer and always engage all but one of said stationary contact members, a selector switch comprising a plurality ot stationary contacts corresponding to the positions of the tap-changer and a rotatable contact for selectively engaging the stationary contacts of said Selector switch, circuit means for interconnecting the stationary contacts of said rotating switch with the corresponding stationary contacts of said selector switch, a timing device, and further circuit means responsive to the timing device for interconnecting, at any given position ot said segments, ali but one of the stationary contacts of said rotating switch and the rotatable contact or" said selector switch with the operating coils of said relays and with a source of energy so that the operating coils of said relays are rendered responsive to the positioning of said rotating switch to thereby etic ct a rotation of said motor in such a direction as to return the tap-changer to a position corresponding to a preselected position ot said selector switch, at which time said rotating switch and said Selector switch cooperate to deenergize said motor.

References Cited in the tile of this patent UNiTED STATES PATENTS 2,516,298 Cage July 25, 1950 2,516,348 Serota July 25, 1950 2,561,220 Ogden July i7, 195i 

